Blueberries are pretty pricey, but they pack a lot of health benefits, making them ideal and popular additions to breakfast cereals and ice cream. That is why some people have become interested in growing their own blueberry bushes. However, they’re challenging to grow and may sometimes turn red.
A blueberry bush turning red means the soil pH is too high or too low, resulting in an inability to absorb nutrients, such as magnesium and phosphorus. A red blueberry bush may also be due to microbial diseases from viruses, bacteria, or fungi, while sometimes, it may just be a natural response to dropping temperatures in fall.
It may seem like a lot of trouble, but don’t feel discouraged about growing blueberries at home. After reading this article, you will find out why your plant is turning red and find some solutions to help fix it.
4 Reasons Why a Blueberry Bush Turns Red
While growing your own blueberry bush at home seems ideal, it’s necessary to remember that this plant has specific requirements for optimum growth. Failure to meet these requirements may negatively affect your plants’ quality and appearance.
Like many other plants, blueberries can express their needs or dissatisfaction in their environment in various ways. One such method is through changes in the color of their leaves and stems. Certain color changes represent specific issues.
Healthy blueberry bushes typically have dark green leaves and branches. The green of the leaves is uniform, without other shades or markings. Mature stems are brown with green branches. Younger stems, on the other hand, are green.
Here are some of the reasons why your blueberry bush is turning red:
1. Incorrect pH
The trickiest part about growing blueberries is the soil pH. They’re best grown in acidic soil with a pH ranging from 4.5 to 5.5. However, some nutrients become unavailable to plants at these levels. Let’s take a look at how pH levels cause the reddening of your blueberry bush:
Very Low pH
An acidic environment is ideal for blueberries, but it can prevent the plant from absorbing essential nutrients, such as calcium, phosphorus, and magnesium.
The lack of phosphorus or magnesium can result in reddish-purple or maroon discoloration of blueberry leaves. Meanwhile, other nutrient deficiencies can result in different symptoms on your plant.
Very High pH
Highly alkaline soil can result from excessive lime or soil amendments to raise the pH because most plants can benefit from slightly acidic or neutral pH levels. The high calcium levels in the soil can result in magnesium deficiency in plants, turning the blueberry leaves red.
Some growers may try to raise the soil pH to achieve a suitable environment for nutrient absorption, but it can be detrimental to the berries. Phosphorus becomes inaccessible to plants at pH levels below 5.5 or above 7.2.
Either way, it’s pretty challenging to find the most suitable pH to meet the blueberry bush’s acidic soil requirement without compromising the accessibility of essential nutrients.
2. Nutrient Deficiency
Plants need many nutrients from the soil to grow. You can pretty much tell which nutrient is lacking by observing the unusual color patterns and changes on your plant’s leaves, stem, or roots.
Nutrient deficiency can be caused by many things, including:
- Lack of organic materials in the soil. Some sterile potting soil may not have sufficient nutrients necessary for your plants’ growth. This is why some gardeners add some fertilizers or compost to supplement the missing nutrients.
- Leaching. Sufficient nutrients may be present in the soil but can be washed away by overwatering. Heavy rain can also push the nutrients deep into the ground, making them inaccessible to the plants’ roots.
- Very low or very high soil pH. Most nutrients are available to plants at optimum soil pH levels ranging from 6.0 to 7.0. Levels below 5.5 or above 7.5 subject the nutrients to chemical reactions, converting them into different forms not readily absorbed by the plants.
Although, not all nutrient deficiencies can turn your blueberry leaves red. Only magnesium and phosphorus deficiency can cause this condition.
Magnesium is vital for chlorophyll production in plants. It also helps with enzyme activities for essential chemical reactions to occur.
Most field soil has enough magnesium to meet your blueberry bushes’ needs. However, the nutrient can easily leach out if the soil is too acidic or during heavy rainfall.
The lack of magnesium can result in chlorophyll shortage, which, in turn, can cause poor growth in plants because of their declined ability to utilize the energy coming from the sun. Chlorophyll also gives the blueberry leaves’ characteristic green color.
Its shortage may cause the interveinal reddening of the leaves. You may observe the reddening mainly in leaves closer to the base of the plant.
Blueberries don’t need much phosphorus, but the lack of the nutrient can result in a reddish-purple tint on their leaves.
Due to the low phosphorus requirement of blueberry bushes, a shortage of this nutrient isn’t a common problem. Which is why most field farmers often don’t pay much attention to it unless the leaves start turning red.
The main reason for the phosphorus-related reddening of blueberry leaves isn’t due to a lack of phosphorus in the soil. Rather, it’s the soil’s acidity, making the nutrient inaccessible to the plant.
As discussed, an acidic environment can cause chemical reactions in the soil, converting phosphorus into forms that cannot be absorbed by plants. Ideally, phosphorus is readily available for plants between pH levels of 6.0 and 7.0, but blueberries thrive best in pH levels between 4.5 and 5.5.
3. Microbial Diseases
Some microbial diseases can also turn the leaves of blueberry bushes red. These diseases occur when the soil is contaminated or some animal vectors and natural factors like wind and air transfer the microbes from one infected plant to another.
Some symptoms of diseases caused by various microbes are similar, making it necessary to diagnose the condition accurately through laboratory tests.
While many viruses can infect your blueberry bush, not all of them can turn the leaves red. You can identify the type of virus that has infected your plant by observing the pattern, location, or degree of redness on the leaves:
- Shoestring: The Blueberry Shoestring Virus (BSSV) causes the blueberry plants to become red and shaped like shoe strings or straps. Other leaves may have oakleaf-shaped red spots stemming from the petioles. Red streaks may also appear on the stems.
- Blueberry scorch: Caused by the Blueberry Scorch Virus (BlScV) spread by aphids. Infected bushes may take one to two years to show symptoms like necrosis and leaf blights and take several years to die completely.
- Sheep pen hill disease (SPHD): Caused by the same virus causing blueberry scorch. Some blueberry cultivars are asymptomatic, but others show red lines forming along the leaf veins. The infection can spread quickly among neighboring plants.
- Red ringspot: Caused by the Blueberry Red Ringspot Virus (BRRV). The red spots first develop on the stems in early summer and spread to the leaves later in the season. It’s distinct from other viral diseases because the discoloration appears only on the upper surface of the leaves.
Bacterial diseases in blueberries are often transmitted to neighboring plants by insects. It can also spread from stem cuttings.
The Blueberry Stunt Phytoplasma bacteria cause this condition. The name comes from the stunted growth infected blueberry bushes exhibit as a result of the infection. Affected leaves develop chlorotic areas that appear brilliant red in the fall.
Leafhoppers usually spread the bacterial pathogen to neighboring plants. The bacteria can also survive in the stems and roots of the plant, making it easy to spread the infection when growing new plants from cuttings.
Bacterial Leaf Scorch
Bacterial leaf scorch disease is caused by the bacterium Xylella fastidiosa. Under this condition, the margins of the leaves develop an oak-leaf pattern. Their darker colored edges begin to lighten to a reddish-brown as the bacterium moves towards the center.
Various fungi thrive in excessively and constantly moist environments, especially when the soil has poor drainage. Fungi also produce spores that can spread to other plants through the wind:
- Leaf rust: The name of the disease comes from the characteristic rust-like appearance of pustules on the lower surface of infected blueberry leaves. The yellow-orange pustules eventually turn red. It’s caused by Pucciniastrum vaccinii.
- Powdery mildew: In midsummer, Microsphaera vaccinii infections in blueberries manifest as a white layer on the upper surface of the leaves. Later in the season, the leaves develop necrotic spots that become deep red.
- Gloeosporium leaf spot: Also known as Anthracnose, this condition is caused by the fungus Gloeosporium minus. Early symptoms appear as tiny red spots on young leaves and stems. Later stages create gray lesions on the leaves.
4. Seasonal Change
It’s natural for blueberry bushes to turn red in the fall due to the dropping temperatures. Depending on the climate conditions during the year, the reddening of the leaves may extend well into early spring until the temperatures become warm enough.
There are no specific temperature ranges to dictate when blueberry leaves turn red in the fall and regain their natural dark green color in the spring. Different areas have varying climate conditions that may affect the blueberries’ overall tolerance and response to the cold.
In addition, different blueberry cultivars or variants may also have varying degrees of reaction to changing temperature conditions.
How To Fix Your Blueberry Bush That Has Turn Red
As noted above, if the red discoloration occurs in the fall, it’s a natural phenomenon, and there’s nothing you can do about it. However, off-season reddening can be alarming.
Once you have determined the main reason for the reddening of your berries’ leaves, you can check out the solutions below:
1. Adjusting Soil pH
When trying to solve the issue of soil pH, you first have to consider the size of the land where you intend to grow your blueberries. If you’re growing them in a vast piece of land spanning acres, it’ll take several months or years to adjust the soil’s acidity to suit your blueberry bushes.
In addition, if the soil in the area naturally has an alkaline pH (over 7.5), it’ll be almost impossible to acidify it and maintain its acidity for a long time. The soil will eventually go back to its alkaline nature. It’ll also be very expensive to try to remedy the situation.
It also helps to remember that you must acidify the soil before planting blueberries and wait at least one full year to see a reaction if any. So if your soil is very alkaline, it may be best to find a different area to grow blueberries or try growing another plant entirely.
Meanwhile, if you intend to grow a blueberry bush in your backyard or containers on your patio, you will have better chances of controlling the soil pH more easily.
Say you have already started growing blueberries and noticed that the leaves are turning red. You must do a soil pH test using a soil pH meter.
If the results read over 7.0, lowering it to an ideal level for your blueberry bush may be difficult. You may need to transplant your berries to a new pot with more acidic soil.
If the issue appears fixable, you can try some of the solutions below:
Lowering the Soil pH
You may select from several ways to acidify your soil:
Apply Sulfur-Based Compounds Like Aluminum Sulfate or Sulfuric Acid
You may also use elemental sulfur. Before adding sulfur products into your soil, you first have to check the pH to determine how much to apply. If the pH is between 6.0 and 7.0, you may lower it using soil acidifiers.
You may want to check out Down to Earth Acid Mix (available on Amazon.com). It’s a natural fertilizer with a 4-3-6 nitrogen, phosphorus, and potassium ratio. It also contains sulfur that can significantly acidify the soil for your berries.
Be sure to check and follow the instructions on the package of soil amendments to receive the best results.
Add Canadian Peat Moss to Your Soil
Canadian peat moss has low pH (around 4.0) and can help acidify the soil significantly if it’s highly alkaline. However, already acidic soil with pH levels below 6.0 might become too acidic when supplemented with Canadian peat moss, so make sure this solution is right for you.
Raising the Soil pH
Using acidic soil amendments risks reducing the soil pH so significantly that plants can’t absorb nutrients anymore. For this reason, you must prepare some ways to reverse the acidity back to acceptable levels:
- Add lime into the soil. It can help raise the soil pH, but it may take some time to see the effects depending on the type of material used. Finer lime granules with high purity or calcium carbonate levels can raise the soil pH faster.
- Spread wood ashes on the soil. Wood ash contains potassium and calcium that can help raise the soil pH. Be sure to apply it with caution as excessive amounts can lead to magnesium deficiency in plants. Spread only a thin layer on the soil surface, ideally every winter.
2. Addressing Nutrient Deficiency
Since the amount of nutrients is not often the problem, adding fertilizers may not always solve the issue. The best fix is maintaining a pH level where blueberries can survive while keeping the nutrients readily available for plants.
Therefore, it’s best to monitor the soil pH every two months and maintain it around 5.5. A routine check is necessary because it takes several months to adjust the pH if it goes beyond the suitable level.
For an immediate fix, though, it’s okay to add fertilizers in the form that plants can readily absorb before they can undergo chemical reactions in the soil.
There are plenty of organic and synthetic sources of phosphorus on the market to address the deficiency in your plants. Some are fast-acting supplements, while others take time to become available for plants’ use.
Here are some excellent phosphorus sources:
Monoammonium Phosphate (MAP) and Diammonium Phosphate (DAP)
You can apply them to the soil once a year since the ammonium parts bind with organic matter while the phosphates can be utilized within 1-5 days.
Another advantage of applying MAP and DAP is that the ammonium component of the compounds may initially raise the pH but will eventually acidify the soil as they undergo nitrification, helping keep the soil acidity at optimum levels.
Composted Manure Is Rich in Phosphorus
It’s easy to find if you live near cattle or poultry farms, which sell excess composted manure for a reasonable price. It also adds more organic matter and nutrients to your blueberries.
However, it may raise the soil pH for a bit to make the condition ideal for phosphorus uptake. Therefore, it’s best to prepare a quick solution to the possible rise in pH levels.
When blueberries suffer from magnesium deficiency, whether due to pH issues or lack of nutrients in the soil, you may apply 3 ounces (85 grams) of Epsom salt around each bush. This salt has magnesium and sulfate, which are both secondary essential nutrients for blueberries.
3. Treating Microbial Diseases
Suppose you have checked the soil pH and the nutritional component of your soil, and neither seems to have any issues that may cause your blueberry bush to turn red. In that case, it may be time to evaluate your plant for a possible risk of microbial infection.
While most infections have unique patterns that can help you identify the root cause of the problem right away, some diseases share similar symptoms. In addition, there may be multiple infections affecting the same plant.
In such cases, it’s best to have your plant undergo laboratory tests for a more definitive diagnosis. It may be costly, but it can help you prevent the spread of the infection if you have numerous blueberry bushes spread across a vast piece of land.
You can collect some samples and have them analyzed. Some samples include:
- Discolored leaves
- Necrotic leaves
- Infected stems
Once the samples have been tested and you have identified the microbe responsible for the disease, you can try the appropriate solutions below:
Viral Infection Treatment
Since aphids generally transmit blueberry viruses, it’s important to use plant-safe pesticides. You have to kill off the aphids before pulling out and destroying infected plants to ensure they don’t transmit the infection to new batches of blueberry bushes.
Infected plants are nearly impossible to save as they primarily manifest symptoms when the infection has already progressed to an incurable level. Therefore, it’s crucial to find infected plants and dispose of them properly by burning them.
The infection also spreads in a radial pattern, which means plants within a 1-kilometer (0.62 miles) radius are most likely also infected. It can be a waste to throw them all out, so you may have all of them tested.
Bacterial Infection Treatment
Leafhoppers, spittlebugs, or sharpshooters often transmit bacterial diseases. Due to this, it’s crucial to monitor the insects’ activities and kill them off with insecticides before destroying the infected plants, in pretty much the same way when dealing with viral infections.
In contrast to viral diseases, bacterial infections do not affect plants in units, groups, or patterns. Instead, they can infect random blueberry bushes in the field.
The good thing is that chances are not many of your blueberry bushes are infected. The bad thing is that you’ll have to test each plant to identify infected ones. Still, the symptoms of bacterial infection appear early on, making it easier to manage before it spreads elsewhere.
Fungal Infection Treatment
Fungal infections may be easier to treat without destroying the plant entirely. You may spray fungicide to the plant. It’s best to check the product’s label before using the chemical as it may affect the quality of your produce.
Depending on the ingredients present in the fungicide, the label would explain the best conditions to apply it to your plant, including the dosage, the timing, the frequency, and safety instructions for the user.
Numerous reasons can turn your blueberry bush red. The reddening may occur on the leaves, young stems, or branches. While it may sometimes be due to seasonal and temperature changes, you must pay attention to off-season changes to possibly fix the issue before it gets worse.
However, it may be tedious and costly to diagnose and treat the causes of the unnatural reddening of your blueberry bushes. Therefore, you must carefully decide whether it’s worth fixing the problem. Otherwise, you can just get a new and healthy blueberry plant entirely.
You can read my other article on blueberry bushes here: How to Improve Soil for Blueberries: 6 Easy Methods